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Abstract Azo dyes with electron-donating and neutral substituents in PMMA matrix and solution were prepared and characterized. High optical quality films were made for linear optical characterization of azo dyes. Two-photon absorption spectra, for investigated compounds dissolved in DMF, were obtained by Z-Scan measurements. The π-π* transition of investigated compounds is significantly red-shifted and overlaps with n-π* transition. Accordingly azo dye with electron-donating group is more red-shifted compared to molecule with neutral group. Refractive index and efficiency of two-photon absorption cross-section for azo dye with neutral substituent is lower compared to azo dye with electron-donating substituent. [ABSTRACT FROM AUTHOR]

Highly oxygen-rich SiOx thin films were prepared using a helicon plasma activated reactive evaporation technique. A small second-order optical nonlinearity was observed in the as-grown films, and thermal poling induced nonlinearity in the films was found to be much larger than that in stoichiometric SiO2 films. These phenomena were associated with the non-impurity defects in the oxygen-rich films. [ABSTRACT FROM AUTHOR]

Abstract: Defects were deliberately induced in SiO x thin films during their deposition using a helicon plasma activated reactive evaporation technique. The films were thermally poled and the poling induced second-order optical nonlinearity was investigated by measuring the second harmonic generation of the samples. It was found that oxygen-rich SiO x thin films containing mainly peroxy radicals enabled a much larger optical nonlinearity than stoichiometric SiO2 films after poling, and their optical nonlinearity was long-time stable; while silicon-rich SiO x thin films containing mainly oxygen vacancy defects presented a smaller and unstable optical nonlinearity after poling. [Copyright &y& Elsevier]